High capacity, high speed, and low power memory is in demand for many different high powered computing systems, such as servers, entertainment distribution head ends for music and video distribution and broadcast, and super computers for scientific, prediction, and modeling systems. The leading approach to provide this memory is to mount a large number of spinning disk hard drives in a rack mounted chassis. The chassis has a backplane to connect to each hard drive and to connect the hard drives to other rack mounted chassis for computation or communication. The hard disk drives connect using SAS (Serial Attached SCSI (Small Computer System Interface)), SATA (Serial Advanced Technology Attachment), or PCIe (Peripheral Component Interface express) or other storage interfaces.
While the spinning disk hard drive provides a large amount of storage at low cost, it has a high power consumption, reliability issues and high heat production. This is not significant for desktop computers with a single drive but when hundreds or thousands of drives are combined, then the power required to drive and cool the disks can be significant. NAND flash drive prices are coming down steadily while reliability and longevity is being improved. As a result, for many applications an AFA (All Flash Array) is used for either hot, warm or cold storage applications or all.
Flash arrays are constructed at high volume in a 2.5″ hard disk drive form factor and in a M.2 module form factor. These form factors have been specifically developed for notebook computers and provide an amount of storage, speed, power consumption and cost that is best suited for notebook computers. An AFA could be built using these standard form factor SSDs (Solid State Drives). When off the shelf 2.5″ SSDs are used for a large capacity solution and they are vertically mounted there is a minimum rack-mount chassis size of 2 U or 3 U due to the size of the drives, the mounting connectors and the need for airflow. M.2 SSDs have a lower capacity and so require many more devices and connectors.